Objectives This study examined the degree to which long workhours in combination with an extended workweek (12 hours/7 days) with permanent day shifts (0700–1900), as requested by the workers, influenced biomarkers for stress, metabolic processes, and diurnal rhythm.

Methods Construction workers (N=50) working 84 hours a week, with alternate weeks off, were compared with construction workers (N=25) having a traditional 40-hour work schedule. The participants were all male and between the ages of 21 to 65 years. Blood samples were obtained in the morning immediately prior to the start of work on workday 1, 5, and 7 to assess cholesterol, cortisol, dehydroepiandrosterone, melatonin, prolactin, testosterone, and uric acid. Psychosocial circumstances were assessed with a questionnaire.

Results The 84-hour group had higher melatonin concentrations and reported higher job-control scores than the 40-hour group. For both groups, the melatonin, cortisol, and cholesterol concentrations were lower on workday 5 than on workday 1. In the 84-hour group, most of the biomarkers were significantly lower in concentrations on workday 7 than on workday 1. Only testosterone showed a significant decrease between workdays 5 and 7. The concentrations of dehydroepiandrosterone and uric acid remained stable across all of the days, as did the melatonin concentrations between workdays 5 and 7.

Conclusions Working of one’s own free will on an 84-hour regimen is not, in the short-term, necessarily more harmful for health than working on a 40-hour regimen with a similar type of heavy worktasks. However, working on an 84-hour schedule beyond the ordinary 40-hour week results in signs of a functional shift in hormonal regulation.